Ion implantation is a property altering process performed in manufacturing, among others, semiconductor devices. Among other tools, a beam-line ion implanter may be used. A block diagram of a conventional ion implanter is shown in FIG. 1. The conventional ion implanter may comprise an ion source 102 that may be biased by a power supply 101. The ion source 102 is typically contained in a vacuum chamber known as a source housing (not shown). The ion implanter system 100 may also comprise a series of beam-line components through which ions 10 pass. The series of beam-line components may include, for example, extraction electrodes 104, a 90° magnet analyzer 106, a first deceleration (D1) stage 108, a 70° magnet collimator 110, and a second deceleration (D2) stage 112. Much like a series of optical lenses that manipulate a light beam, the beam-line components can manipulate and focus the ion beam 10 before steering it towards a target workpiece. During ion implantation, a wafer 114 is typically mounted on a platen 116 that can be moved in one or more dimensions (e.g., translate, rotate, and tilt) by an apparatus, sometimes referred to as a “roplat” (not shown).
In operation, the ions are generated in the ion source 102 and extracted by the extraction electrodes 104. The extracted ions 10 travel in a beam-like state along the beam-line components and implanted to the wafer 114.
As noted above, the ion implantation process is a property altering process. For example, ions such as boron and phosphorous ions may be implanted to portions of a silicon wafer to change electrical properties of the wafer. A field effect transistor is an example of a device that may utilize the above implantation. As known in the art, such implantation may enhance the electrical property of the wafer.
The ion implantation process may also be performed to enhance other properties, such as optical and mechanical properties. For example, the ion implantation process may be performed to destroy crystallinity of a crystal substrate, thereby limiting crystalline slips and enhancing mechanical toughness of the substrate. In addition, the process may be performed to reduce diffusion rate or mobility rate of ions implanted within the substrate.
As the properties of the final product may depend on the parameters of the property altering ion implantation process, it may be desirable to control the parameters of the implantation process. One of such parameters may be the angle by which the ions are directed to the wafer. The ion angle may be important as the angle may determine the size and/or location of the implanted region. In addition, the ion angle may influence the depth of the implantation. For example, ions that are directed at an angle perpendicular to the wafer may be implanted at a greater depth than ions that are directed at other angles. If the ions are directed toward the substrate in multiple, non-uniform angles, ions may be implanted at different depths and the implantation may be non-uniform. Further, the angle of the ions may be an important parameter as the three dimensional device substrates may include surfaces oriented at different angles (e.g. vertical and horizontal surfaces). Ions directed toward the substrate at one angle may reach one surface, but may not reach another surface.
Another important parameter may be the ion dose. It may be desirable to control the ion dose such that the processed product may meet the required electrical property. Controlling the ion dose may also be important to produce uniform devices. For example, it may be desirable to control the ion dose such that several devices manufactured from a single semiconductor substrate may have uniform properties. In addition, controlling the ion dose may be desirable, as devices manufactured from different substrates may have uniform properties.
One of the tools used to measure and control the ion dose is a Faraday cup 200 shown in FIG. 2. A conventional Faraday cup 200 may comprise a Faraday cup body 22, defining an empty region 24. The Faraday cup body 22 includes an end wall 22a and side walls 22b. The Faraday cup 20 may further include a housing 26 that encloses the Faraday cup body 22. The housing 26 may include a front plate 28 having an opening that defines an entrance aperture 30 of the chamber 24. The Faraday cup body 22 may be connected to a dose processor.
The Faraday cup body 22 may receive the ions and generates an electrical current representative of the ion dose. The current is then input to the dose processor. By measuring the dose, the components of the ion implanters may be adjusted to produce ions conforming to a desired specification.
Although the Faraday cup 20 illustrated in FIG. 2 is capable of detecting the ion dose, the cup 20 is incapable of measuring other characteristics of the beam. Therefore, there is a need for a new apparatus.